This nonprovisional application claims priority under 35 U.S.C. xc2xa7 119(a) on Patent Application No. 2001-219319 filed in Japan on Jul. 19, 2001, the entirety of which is hereby incorporated by reference.
1. Field of the Invention
This invention relates to a supercharger cooling structure for a small watercraft.
2. Description of Background Art
The power source in widespread small watercrafts (for example, personal watercrafts(PWCs)) conventionally is a 2-cycle engine. However, it has been examined to use a 4-cycle engine for the power source in order to cope with the reduction of pollution in recent years.
However, the output power of a 4-cycle engine is lower than that of the 2-cycle engine of the same total stroke volume. Accordingly, it has been examined to incorporate an engine with a supercharger in order to make up for the loss of power. The assignee of the present application has proposed a small watercraft, in which an engine with a supercharger is incorporated, in Japanese Patent Laid-Open No. 2001-140641.
In the small watercraft 1 disclosed in the above document, a 4-cycle engine 2 with a supercharger 3 is incorporated in the inside of a body 1 as shown in FIGS. 11 and 12 of the present invention.
As shown also in FIGS. 13 and 14 of the present invention, an exhaust manifold 4 is provided on the left side of the 4-cycle engine 2 in an advancing direction F of the body 1. An intake chamber 5 is provided on the right side of the 4-cycle engine 2.
Exhaust gas from an exhaust gas exit 4a of the exhaust manifold 4 is introduced into a turbine portion 3T of the supercharger 3. Compressed air from a compressor portion 3C of the supercharger 3 is supplied into the intake chamber 5 described above through an intercooler 6.
A cooling structure for the supercharger 3 is such that cooling water from a cooling water output port of a jet pump 7 driven by the engine 2 is supplied, through a cooling water hose (not shown) from a water entrance 4b (refer to FIG. 13) of the exhaust manifold 4 into a water jacket in the exhaust manifold 4. The water having cooled the exhaust manifold 4 is supplied from a cooling water exit 4c of the exhaust manifold 4 through a hose (not shown) into a water jacket in the supercharger 3 from a water entrance 3a (refer to FIG. 14) of the supercharger 3 to cool the supercharger 3.
In the background art described above, water having cooled the exhaust manifold 4 is introduced into the supercharger 3 to cool the supercharger 3. Accordingly, there is a problem in that the supercharger 3 cannot always be cooled sufficiently.
The object of the present invention resides in a solution of such a problem as described above to provide a supercharger cooling structure for a small watercraft which can cool the supercharger sufficiently.
In order to attain the object described above, according to a first aspect of the present invention, a supercharger cooling structure for a small watercraft in which an engine with a supercharger is incorporated includes cooling water from a pump being supplied to the supercharger through a different supercharger cooling water passage independent of any other cooling water passage.
According to a second aspect of the present invention, the supercharger cooling structure for a small watercraft according to the first aspect of the present invention includes the cooling water from the supercharger cooling water passage being first supplied to the supercharger to cool the supercharger and then supplied to an exhaust system provided downstream from the supercharger in an exhaust system for the engine.
According to a third aspect of the present invention, the supercharger cooling structure for a small watercraft according to the first and second aspects of the present invention includes the cooling water having cooled the supercharger being supplied to an exhaust pipe provided downstream from the supercharger in an exhaust system and is then discharged to the outside of the watercraft together with exhaust gas.
According to a fourth aspect of the present invention, the supercharger cooling structure for a small watercraft according to the first through third aspects of the present invention includes oil supplied to the supercharger. The oil is used for lubrication of a bearing portion of the supercharger and is supplied to an oil jacket formed in a bearing casing to cool the bearing casing.
With the supercharger cooling structure for a small watercraft according to the first aspect of the present invention, the small watercraft, in which the engine with a supercharger is incorporated, is structured such that cooling water from the pump is supplied to the supercharger by the different supercharger cooling water passage independent of any other cooling water passage. Accordingly, the supercharger can be cooled efficiently and sufficiently.
With the supercharger cooling structure for a small watercraft according to the second aspect of the present invention, the cooling water from the supercharger cooling water passage is first supplied to the supercharger to cool the supercharger and is then supplied to the exhaust system provided downstream from the supercharger in the exhaust system for the engine. Accordingly, in addition to the advantages of the first aspect of the present invention, the supercharger can be cooled with cooling water in a state having a low temperature. Accordingly, the supercharger can be further cooled efficiently and sufficiently. Furthermore, the exhaust system provided downstream from the supercharger can be cooled.
With the supercharger cooling structure for a small watercraft according to the third aspect of the present invention, the cooling water having cooled the supercharger is discharged to the outside of the watercraft together with exhaust gas after it is supplied to the exhaust pipe provided on the downstream with respect to the supercharger in the exhaust system. Accordingly, the exhaust gas which has driven the supercharger is further cooled in the exhaust pipe.
In other words, since the exhaust gas is cooled in the supercharger and the exhaust pipe, the exhaust gas energy can be reduced synergetically. As a result, the exhaust noise can be reduced.
With the supercharger cooling structure for a small watercraft according to the fourth aspect of the present invention, oil is supplied to the supercharger. The oil is used to lubricate the bearing portion of the supercharger and is supplied to the oil jacket formed in the bearing casing to cool the bearing casing. Accordingly, the supercharger can be cooled more efficiently.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.